Hepatitis C Virus (HCV) is able to establish chronic infection in the face of robust anti-viral interferon signaling. Moreover, the virus can persist at undetectable levels during interferon alpha treatment only to reemerge, causing breakthrough and relapse in patients. My thesis research demonstrates that HCV forms a genome-length double-stranded RNA (dsRNA) in response to interferon, and tested the hypothesis that this non-replicative dsRNA acts as a genomic reservoir that allows HCV relapse to occur. Novel methods were developed to quantify long dsRNA. These methods revealed that the majority of HCV RNA in human liver is in double-stranded form. The abundance of HCV dsRNA correlated with interferon-stimulated gene induction. In a cell culture model of HCV infection, treatment with interferon alpha induced the formation of genome-length HCV dsRNA. This was dependent of the activity of the HCV polymerase, indicating that production of HCV dsRNA required de novo synthesis. The induction of HCV dsRNA correlated with phosphorylation of protein kinase R (PKR), a dsRNA recognition protein that becomes phosphorylated upon binding of dsRNA. Ribavirin, a drug used to prevent relapse, blocked the interferon-induced production of viral dsRNA and reduced the extent of PKR phosphorylation. Interferon treatment was not the only experimental procedure that increased HCV dsRNA. Rather, the concentration of this species also increased in cells grown at high density and unfed over a 6-day period. Significantly, the dsRNA reentered the productive replication cycle when favorable conditions were restored. The most important finding of my research is that HCV is able to produce a highly stable genome-length dsRNA that may be an important viral countermeasure to host interferon-mediated antiviral defenses. Targeting viral dsRNA by ribavirin, and other anti-viral drugs, may be an effective pharmaceutical strategy.
|Advisor:||Branch, Andrea D.|
|Commitee:||Chen, Benjamin, Cortes, Patricia, Rosenberg, Brad, Simon, Viviana, tenOever, Benjamin|
|School:||Icahn School of Medicine at Mount Sinai|
|School Location:||United States -- New York|
|Source:||DAI-B 77/01(E), Dissertation Abstracts International|
|Subjects:||Molecular biology, Virology, Immunology|
|Keywords:||Double-stranded rna, Hepatitis c virus, Interferon, Relapse, Ribavirin|
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